When a person wishes to meet a friend at a crowded place such as an event site or, the person wishes to reunite with the friend who got separated at the event site, the person may use a portable telephone and call the friend in order to meet or reunite with the friend. The person may communicate with the friend using their portable telephones, and the two may notify their respective current positions. However, even when a common landmark or the like is located near their current positions, it may be difficult for the two to immediately recognize each other's current positions.
On the other hand, a portable telephone equipped with the GPS (Global Positioning System) may acquire the current position of the portable telephone. Hence, the user of such a portable telephone may send the current position acquired by the GPS to the friend also using such a portable telephone, so that the two may recognize their respective current positions. The user may use his own current position and the current position of the friend, in order to move to the current position of the friend.
However, it may be difficult for the portable telephone equipped with the GPS to acquire the current position when the portable telephone is at a location where it is difficult for radio waves to reach the portable telephone, such as indoors. When an error in the current position of the portable telephone acquired by the GPS is large due to a poor radio wave reception state, it may be impossible for the user to meet or unite with the friend even when the two communicate using their portable telephones. Even outdoors, the GPS may be unable to accurately detect a positional error on the order of several meters, for example, depending on the radio wave reception state. For this reason, the person may not be able to meet or reunite with the friend even when the distance between the two is on the order of 15 meters, for example, and relatively close. The positional error of the GPS may be larger near buildings due to interference, and in this case, it may be difficult for the person and the friend to meet or reunite outdoors in the crowd.
On the other hand, an information processing apparatus equipped with a GPS has been proposed to acquire position information indicating the current position, and to additionally acquire direction information indicating the direction in which the information processing apparatus is facing, and distance information indicating the distance from the information processing apparatus to a predetermined position. This proposed information processing apparatus includes a function to compute position information indicating a predetermined target position, based on the acquired position information, direction information and distance information. However, this proposed information processing apparatus may not function effectively when accurate position information cannot be acquired by the GPS due to poor radio wave reception state, and it may be difficult for the person and the friend to meet or reunite in the crowd using such proposed information processing apparatuses.
A portable telephone equipped with a magnetometer or attitude sensor has also been proposed. This proposed portable telephone measures the direction in which the portable telephone is currently facing, based on the earth magnetism measured by the magnetometer, and sends the measured result to the friend's portable telephone. The friend's portable telephone also sends the direction in which the friend's portable telephone is currently facing, based on the measured earth magnetism. Hence, the proposed portable telephone may use its facing direction and the friend's facing direction received from the friend's portable telephone, in order to judge whether the two are facing each other and send the judgement result to the friend's portable telephone. Such a communication may be continued to enable the two to meet or reunite even in the crowd. However, the proposed portable telephone merely enables the two to recognize the direction in which the other party is currently located, and there is no way of knowing the distance separating the two. In addition, the direction in which the person is facing and the direction in which the portable telephone is facing must match, and the direction in which the friend is facing and the direction in which the friend's portable telephone is facing must match, in order for the two to recognize each other's direction. Consequently, it may be difficult for the person and the friend to meet or reunite in the crowd using such proposed portable telephones.